U.S. patent number 5,343,368 [Application Number 08/009,313] was granted by the patent office on 1994-08-30 for thermally neutral portable power sources.
This patent grant is currently assigned to Welch Allyn, Inc.. Invention is credited to William R. Miller.
United States Patent |
5,343,368 |
Miller |
August 30, 1994 |
Thermally neutral portable power sources
Abstract
A passive thermal mechanism for controlling the environmental
temperature of a device having a battery and heat producing load
contained within a portable housing so that the housing will remain
in a thermally neutral condition and the battery will be maintained
in an optimum operating condition.
Inventors: |
Miller; William R. (Skaneateles
Falls, NY) |
Assignee: |
Welch Allyn, Inc. (Skaneateles
Falls, NY)
|
Family
ID: |
21736891 |
Appl.
No.: |
08/009,313 |
Filed: |
January 22, 1993 |
Current U.S.
Class: |
362/572; 362/183;
429/120; 362/294; 362/373; 165/902; 62/3.3; 362/261 |
Current CPC
Class: |
F21V
29/00 (20130101); G02B 6/4296 (20130101); F25B
21/02 (20130101); F21L 4/08 (20130101); H01M
10/615 (20150401); Y10S 165/902 (20130101); H01M
10/643 (20150401); G02B 6/4298 (20130101); Y02E
60/10 (20130101) |
Current International
Class: |
F21V
29/00 (20060101); G02B 6/42 (20060101); F21L
4/00 (20060101); F21L 4/08 (20060101); F25B
21/02 (20060101); H01M 10/50 (20060101); H01M
10/42 (20060101); F21V 008/00 (); F21V
029/00 () |
Field of
Search: |
;362/32,183,208,261,264,294,373 ;219/202,203 ;320/35,36 ;429/120
;62/3.2,3.3 ;165/47,902 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Yeung; James C.
Assistant Examiner: Cariaso; Alan
Attorney, Agent or Firm: Harris Beach & Wilcox
Claims
What is claimed is:
1. A portable device that includes a housing,
an energy source mounted within said housing,
an energizeable load mounted within said housing being connected to
said energy source which when energized converts at least some of
the source energy into heat,
thermal means disposed entirely in said housing, said thermal means
being in heat transfer relationship with the load and the housing
that contains a phase change material which changes state at a
desired temperature to maintain the housing in a thermally neutral
condition wherein the housing neither rejects or accepts heat
energy from its surrounding environment, and
means for initializing the phase change material to a desired
state.
2. The device of claim 1 wherein the phase change material changes
state at a temperature between 70.degree. F. and 98.degree. F.
3. The device of claim 1 wherein the thermal means is placed in
thermal communication with both the energy source and the load.
4. The device of claim 1 wherein the energy source is a battery and
the load is a lamp.
5. The device of claim 4 wherein said lamp is a high intensity arc
lamp.
6. The device of claim 5 that further includes a reflector means
for focusing the light output of said lamp at a focal point.
7. The device of claim 6 that further includes means for
positioning a light entrance face of a fiber bundle at the focal
spot of the reflector.
8. The device of claim 1 that further includes a switch means for
selectively energizing said load.
9. A portable device that includes
a housing,
a battery mounted within said housing,
an energizeable load also mounted within said housing that is
connected to said battery which, when energized, converts at least
some of the battery energy into heat,
a first inner thermal means disposed entirely in said housing, said
first inner thermal means being in thermal communication with the
battery that contains a first phase change material that changes
state at a first desired temperature to maintain the battery at an
optimum operating temperature,
a second outer thermal means disposed entirely in said housing,
said second outer thermal means being in thermal communication with
the load and the housing which contains a second phase change
material that changes state at a second desired temperature to
maintain the housing at a thermally neutral condition wherein the
housing neither rejects nor accepts thermal energy from its
surrounding ambient, and
means for initializing said first phase change material and said
second phase change material to a desired state.
10. The device of claim 9 that further includes insulation means
for thermally isolating said first and second thermal means.
11. The device of claim 9 wherein said lamp is a high intensity arc
lamp.
12. The device of claim 9 that includes terminal means for
recharging the battery.
13. In combination,
a portable device having a housing, a rechargeable battery within
said housing that is connected to a load that converts at least
some of the battery energy to heat and thermal means containing a
phase change material that changes state at a desired temperature
that is in thermal communication with the load and the housing
whereby the housing is maintained in a thermally neutral condition
so that it neither rejects nor accepts energy from its surrounding
ambient as the material changes state,
a charging stand for removably receiving said housing,
a first coacting means in the stand and the device for charging
said battery when said housing is received within said stand,
and
a second coacting means in the stand and the device for placing the
phase change material in communication with a heat pump means
within the stand for initializing the phase change material to a
desired state when the housing is received within said stand.
14. The combination of claim 13 wherein said device contains a
second thermal means positioned inside the first thermal means said
second thermal means being in thermal communication with said
battery and containing a second phase change material that changes
state at the optimum operating temperature of 'the battery and
further including
a third coacting means in the stand and the device for placing the
second phase change material in communication with a second heat
pump means in the stand for initializing the second phase change
material to a desired state when the housing is received within the
stand.
15. A method of maintaining a thermally neutral environment in a
portable device comprising the steps of:
disposing an energy source in a housing;
mounting an energizeable load within said housing;
connecting said energizeable load to said energy source, which when
energized converts at least some of the source energy into
heat;
disposing a first thermal means entirely in said housing, and
placing said first thermal means in heat transfer relationship with
the load and the housing;
placing a first phase change material in said first thermal means,
said first phase change material changing state at a desired
temperature to maintain the housing in a thermally neutral
condition, wherein the housing neither rejects or accepts heat
energy from its surrounding environment; and
initializing the first phase change material to a desired state
with a heat pump.
16. The method in accordance with claim 15, wherein said energy
source comprises a battery and said load comprises a high intensity
arc lamp.
17. The method in accordance with claim 16, further comprising the
step of:
while said step of initializing the first phase change material is
being performed, recharging said battery.
18. The method in accordance with claim 15, further comprising the
steps of:
disposing a second thermal means entirely in said housing, said
second thermal means being in thermal communication with the load
and the housing;
placing a second phase change material in said second thermal
means, said second phase change material changing state at a second
desired temperature; and
initializing the second phase change material to a desired state
with a heat pump.
Description
BACKGROUND OF THE INVENTION
This invention relates to passive apparatus for thermally
controlling the environment of a portable device.
One embodiment of the invention involves a portable light box
containing a battery and a high intensity lamp connected thereto
which generates heat. Such a portable light box is used in the
medical arts to provide light via a fiber bundle to endoscopic
devices, such as a rhinolaryngoscope or the like, and surgical
headbands of the type worn by physicians during various types of
medical procedures. The light box is typically carried by the user
in a pocket of a laboratory jacket or clipped to the user's belt.
With constant usage, the light box can become overly warm, and thus
uncomfortable when carried close to the body.
Battery operated equipment, such as the light box noted above, may
also be exposed to changing outdoor conditions. Temperature
extremes of both hot and cold can considerably shorten the useful
life of the battery. Failure of the battery, and thus the equipment
powered by the battery, can pose a danger under certain field
conditions.
SUMMARY OF THE INVENTION
It is therefore a primary object of the present invention to
improve portable, battery operated devices.
It is a further object of the present invention to improve
portable, battery operated devices that can be thermally impacted
during operation.
A still further object of the present invention is to provide a
passive mechanism for controlling the environment surrounding a
portable device containing a heat producing load so that the device
can be worn comfortably on the user's person.
Another object of the present invention is to provide a battery
operated device with a rechargeable, passive mechanism for
thermally maintaining the temperature of the battery within a
desired operating range.
Yet another object of the present invention is to provide a
passive, thermally-controlled, portable device and a recharging
stand for receiving the device for resetting the passive control
medium.
These and other objects are attained in one embodiment of the
present invention by means of a portable light box having a housing
in which is contained a heat producing lamp that is connected to a
battery. A phase change material is placed in thermal communication
with the lamp which changes state at or near some pre-selected
temperature, e.g. room or body temperature. The material absorbs
heat produced by the lamp to maintain the housing in a condition
such that the light box can be comfortable worn or carried by the
user without the need of venting heat to the surrounding ambient,
The phase change material may also be placed in thermal
communication with the battery to maintain the battery at an
operating temperature which affords maximum battery efficiency.
In another embodiment of the invention, the battery is placed in
thermal communication with a first phase change material that
changes state at a first temperature and the lamp is placed in
thermal contact with a second phase change material that changes
state at a second temperature. The phase change materials are
selected to provide for optimum lamp cooling and battery operation.
Suitable phase change materials are well known. For example in U.S.
Pat. No. 4,709,752 the following are disclosed:
CH.sub.3 COONa.multidot.3H.sub.2 O, melting-point 58.degree. C.,
heat of fusion 289 kJ/dm.sup.3 ;
NaOH.multidot.H.sub.2 O eutect., melting-point 61.degree. C., heat
of fusion 336 kJ/dm.sup.3 ;
NaOH.multidot.H.sub.2 O congr., melting-point 64.degree. C., heat
of fusion 378 kJ/dm.sup.3 ; and
CaCl.sub.2 .multidot.6H.sub.2 O, melting-point 30.degree. C., heat
of fusion 284 kJ/dm.sup.3.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of these and other objects of the
present invention, reference will be made to the following
description of the invention which is to be read in conjunction
with the following drawings, wherein:
FIG. 1 is a perspective view of a portable, battery operated light
box embodying the teachings of the present invention showing the
device mounted within a recharging stand, and
FIG. 2 is a side elevation, in section, taken along lines 2--2 in
FIG. 1 showing further features of the light box and the charging
stand.
DESCRIPTION OF THE INVENTION
Referring now to the drawings, there is shown a portable light box
12 and recharging stand assembly, generally referenced 10, that
embodies the teachings of the present invention. The light box 12
includes an enclosed housing 14 that contains a lamp 15 mounted
within a reflector 16. The lamp is electrically coupled to a
rechargeable battery 17 by means of a pair of electrical leads 18
and 19. A switch 20 is mounted in the side wall of the light box
housing which serves to open and close the circuitry supplying
power to the lamp, Although some of the energy provided to the lamp
is converted to a light output, most of the energy is lost in the
form of heat.
Lamp 15 is preferably a high intensity, low wattage arc lamp of the
type described in U.S. Pat. Nos. 5,117,154 and 5,138,228, the
disclosures of which are incorporated herewith by reference. These
new high intensity arc lamps exhibit extremely long life and
provide a high light output per watt that makes them ideally suited
for use in medical and other applications. As shown by the phantom
lines in FIG. 2, the reflector is arranged to focus the light
output of the lamp at a point 25 at the entrance to a cylindrical
guide 27 mounted in the top of the housing 14. The cylindrical
guide is arranged to slidably receive therein a fiber bundle 29 for
transmitting light energy to a surgical headband or an endoscopic
device (not shown) requiring a high intensity light input. The
fiber bundle is equipped with a radially extended stop 30 that
coacts with the top surface of the cylindrical guide to position
the light entrance face 31 of the bundle in the plane of focal
point 25, As a result of this construction, a preponderance of the
visible light energy emitted by the lamp will pass into the bundle
and thus be delivered into the desired target area, The remainder
of the light energy is retained within the housing in the form of
heat.
As best seen in FIG. 2, the battery 17 is surrounded by an inner
blanket 40 containing a first phase change material 41. The blanket
is designed to place the phase change material in thermal contact
with a major portion of the battery surface area, The phase change
material 41 is selected so that the material will change state at
about the optimum operating temperature of the battery,
The term phase change material is herein used in reference to a
material that will change from one state to another at a constant
temperature. As it changes from a solid state to a liquid state,
the material will absorb energy equal to its latent heat of fusion.
Similarly, as the phase change material changes from a liquid to a
solid state, it will give up or reject heat into the battery that
is equal to its latent heat of solidification. In the event the
battery is to be exposed to low outdoor temperatures, that is
temperatures below the normal phase change temperature of the
material, the material will initially be heated to place it in a
liquid state. The material will thus be able to reject the stored
latent heat of solidification into the battery to keep the battery
warm. The warming will continue until such time as the material has
completely changed its phase to its solid state thus maintaining
the battery at a desired operating temperature for an extended
period of time.
Similarly, when the battery is exposed to higher than desired
operating temperatures, the phase change material is initially
refrigerated to place it in a solid state. As a consequence, the
material is able to absorb heat from the battery as it changes to a
liquid state to again maintain the battery at a desired operating
temperature.
The inner side walls, end walls and top wall of the light box
housing are covered with a second outer thermal blanket 33 which
contains a second phase change material 35 that is selected so that
it will change state at about a comfortable body temperature. The
second phase change material is in thermal communication with the
arc lamp 15 and the lamp enclosure. As noted, energy not converted
to light energy will remain in the housing in the form of heat. If
permitted to build up, this energy can warm the housing to a point
where it will cause the user discomfort if carried close to the
body, as for example, when carried in a pocket or suspended from a
belt. The second phase change material is initially refrigerated to
place it in a solid state. The cooled material is able to absorb
heat from the lamp as it changes phase to a liquid state. The
second phase change material is selected so that it will maintain
the housing at a user comfortable temperature between 70.degree. F.
and 90.degree. F. during the phase change. As should be evident,
this passive cooling effect takes place without the need of outside
ventilation or the like. The second blanket will keep the housing
in a thermally neutral condition wherein it will neither reject nor
accept heat energy from the surrounding environment.
A layer of insulation 43 is placed between the inner and outer
temperature control blankets thus permitting the battery and
housing temperatures to be controlled independently.
As shown in the drawings, the portable light box is receivable in a
well 50 formed in the recharging stand. The stand is equipped with
a pair of thermoelectric heat pumps 51 and 53 which serve to place
the phase change materials to a desired initial state, The upper
heat pump 51 is placed in thermal communication with the outer
temperature control blanket 33 through means of a highly conductive
metal plate 55 situated in the side wall 56 of the light box
housing. A pair of resilient pads 57 and 58 mounted on the opposing
wall of the well urge the plate 55 into intimate contact with the
outer heat transfer surface 60 of heat pump 51,
When the light box is placed in the well, heat pump 51 is
automatically cycled on by the electrical control circuitry 62 to
draw heat from the outer blanket, The heat is rejected by the heat
pump into passageway 63 and then passed to the surrounding ambient
by means of a motor driven fan 65,
The lower heat pump 53 is similarly placed in thermal communication
with the inner thermal control blanket 40 through means of a second
highly conductive plate 68 mounted in the floor of the housing.
Heat pump 53 can be selectively cycled through the electrical
control circuitry to either heat or cool the phase change material
stored in the inner temperature control blanket, depending upon
existing ambient conditions. As noted above, the phase change
material will change state at a constant desired temperature to
maintain the battery at a desired optimum operating condition.
The lower heat pump is mounted in a horizontally disposed
passageway 70 having a side wall vent 71 that allows ambient air to
freely reach the heat pump outer heat exchange surface 72.
A pair of battery terminals 75 and 76 are located in the side wall
of the light box housing and are connected to the battery by
suitable leads. The terminals are arranged to cooperate with a pair
of sliding contacts 77 and 78 mounted in the side wall of the well
of the recharging stand to connect the battery with the stand's
electrical control circuitry when the light box is fully seated in
the well, The control circuitry is programmed to bring the battery
up to full charge and maintain it in this condition as long as the
light box remains in the stand.
While this invention has been explained with reference to the
structure disclosed herein, it is not confined to the details set
forth and this application is intended to cover any modifications
and changes as may come within the scope of the following
claims:
* * * * *